Technical Field
The invention relates to a method for detecting failure of soft start and a variable frequency device.
Related Art
Motor is an electrical device which can convert electrical power into mechanical power so as to drive other devices. Motors can be applied to for example industry huge motor, home fan motor, even or small or mini motor for mobile device, etc. Motor promotes the progress of technology and it is really convenient.
However, in the energy conversion of the motor, because partial electrical energy is converted into heat and consumed, the resulted mechanical energy is less and thus the conversion efficiency of energy is lowered. Thus, some industries utilize the inverter to drive the motor to adjust the frequency and amplitude of operating voltage so as to control the revolution and torque of the motor to improve conversion efficiency of power.
The inverter contains a soft start device and utilizes the resistor and the relay for soft start to prevent the elements from the damage due to the surge current generated by the input voltage. But when the soft start device fails and outputting to a load still continues, the resistor for soft start may easily catch fire due to overly high temperature.